 |
 |
 |
 |
||
  |
|
|
#151
2nd July 2008, 16:25
|
|||
|
|||
|
Quote:
Do you know the AOA numbers of other fighter aircrafts? *http://www.canit.se/~griffon/aviation/gripen/ Quote:
   
|
|
#153
2nd July 2008, 22:30
|
||||
|
||||
|
Quote:
|
|
#154
2nd July 2008, 22:35
|
||||
|
||||
|
Quote:
I do not know in detail the numbers but for example the Viggen can over pass more than 30 degrees for sure but only in experimental tests the Viggen can be flown confortably up to 25 deg of AoA and only beyond 38 deg of AoA it will experiment departure tendencies. http://ntrs.nasa.gov/archive/nasa/ca...1987013196.pdf   Last edited by MiG-23MLD; 2nd July 2008 at 22:46.
|
|
#155
3rd July 2008, 02:54
|
|||
|
|||
|
I donno where JDW got this info from but the LCA has far surpassed the 17 deg limit (under certain conditions....while JDW seems to be propagating this fallacy as a blanket statement). As Nitin used to say, don't pay attention to such "drivel".
There are certain issues with the "flight envelop" and that's why Boeing is being brought in, it has to do with the fact that Indians have no experience with this aspect of the flight and it was always a bridge that was to be crossed when they came to it. And like I have stated before...its better to pay Boeing a couple of million rather than have a disaster on their hands when they go into "this phase of validation of the flight envelop". There are enough an more oracles on this forum that will hang the LCA to dry and we can see JDW trying to force "17 deg" fatwa on us, imagine what would happen if there was a real incident.
|
|
#156
3rd July 2008, 03:13
|
|||
|
|||
|
Firstly, it may be reiterated that as per the links posted by 21Ankush and myself earlier, it has been reported that canards were added, but later cancelled on the Naval Tejas as CFD flight-tests did not indicate enhancement in lift, stability or manoueverability.
Quote:
Another explanation may be that suppose Rafale or J-10 needs to bank while executing a pitch. Thus, the canards will be deployed for pitch and the airelons for thr bank; had they been elevons acting in concert with canards, this manouever may not be possible. Quote:
In this photo of Eurofighter, the canards are "drooped" as in 'A' and not in 'V' (the 'V' orientation is usually seen when J-10 is taxiing). In the photos off J-10 while in flight, the canards are not necessarily seen to be "upright". To generate lift, they have to "droop", which in turn may increase 'wash' over the wing. Quote:
It must be noted that elevons are also significantly "bigger" than canards as they span a larger width as seen in this video posted by 21Ankush. Thus, their effect on lift cannot be much lower than canards. As regards the landing distance of Gripen, it is true that it is configured to land on civilian highways also, which indicates a short-takeoff and landing capability. However, it may also be assisted due to parachutes, large flaps, etc.
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A. Last edited by Abhimanyu; 3rd July 2008 at 03:17.
|
|
#157
3rd July 2008, 14:17
|
||||
|
||||
|
Quote:
If you rate the Asian fighters by capabilities you will get something like this The best all around fighters are F-22 and F-35 The second best are Su-35BM and Eurofighter Typhoon in third place you get the Su-30MKI, Rafale, F-18E. fourth place are the Gripen, MiG-35, J-10, F-16I/F. fifth place are the LCA, MiG-29A, Su-27B, F-15E/F-15C, Mirage 2000, F-16C/F-2 and F-18C. Sixth place are the FC-1, Ching Kuo and Probablythe Iranian fighter Saeqeh-fighter The rest do not count any more since are basicaly absolete among them is the J-8II totally outclassed or the MiG-23 and MiG-25 The LCA is not in the class of the J-10 for sure, still the aircraft is not as good, the LCA deleted the canards simply because of weight considerations but the J-10 still is a very advanced proposition on par with the best fourth generation fighters, the LCA is only competitive in terms of avionics and weaponry but not in aerodynamics. It is true, the LCA can defeat the J-10 for sure with good avionics and missiles coupled with good tactics, however as far as to say canards are not giving control to the J-10 in AoA and turn rate is something is not true, the Eurofighter and Su-30MKI have canards for something and only the Su-35 has deleted them because the 117S is the best engine in the world in terms of thrust vectoring and supercruise  Even a F-16s with Python V can beat the J-10 but in agility very likely is not as good, only the Gripen probably beats it without missiles  while the F-18E is not as agile as the MiG-35 or J-10 still carries a puch in AIM-120 and AIM-9Xs able to deal with the enemy. The MiG-35 still needs to be purchased with Thrust vectoring to be on par with the Eurofighter. The Rafale and Su-30MKI since are big versions of the Gripen and MiG-29OVT still carry more weaponry than their smaller cousins Last edited by MiG-23MLD; 3rd July 2008 at 14:44.
|
|
#158
3rd July 2008, 19:26
|
|||
|
|||
|
Earlier I mentioned that landing distance of Gripen on civilian highways is short as it may use parachutes and flaps. However, flaps themselves are subject to "wash". To offset it, canards are used in a near vertical position as shown in this photo of Gripen while it is taxiing.
MiG-23 MLD, in this "era" avionics may not matter much, as even JF-17 is scheduled to be installed with an AESA radar and state-of-the-art European avionics suite. Thus avionics are like "plug-ins", and the platform in which they are installed --- whether JF-17 or Typhoon --- may be immaterial. However, it can be safely mentioned that structurally and aerodynamically, Tejas is at par with the Typhoon as it is an unstable design, it is controlled by a flight-control system (that also controls the slats on each wing's leading edge), and a high percentage of composites. As shown in the video posted by 21Ankush, Tejas can perform the entire range of manouevers with agility and speed. Now regarding the Su-30 MKI, it has small canards that are fixed, and which are not in the pilot's control. They trim automatically according to the receipt of airflow. The pitch authority remains on the rear tails. I think Su-30 MKI is the only plane to have canards as well as tails.
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A.
|
|
#159
3rd July 2008, 20:43
|
|||
|
|||
|
Quote:
To MIG-23MLD 
|
|
#160
4th July 2008, 00:33
|
||||
|
||||
|
Quote:
The LCA won`t be able to out maneuvre more modern fighters in my opinion, the Eurofighter is probably the fourth best fighter in the world, i rate it on par to the Su-35BM simply because both have the following technologies, supercruise and supermaneouvrability. The SU-30MKI has moveable canards see  see they are used as yaw and pitch devices  http://www.airwar.ru/fighternow.html However the Su-30 is a heavy fighter weighing more than twice a LCA at fully load, so the canards are not a big burden to the Su-27 which already weighs almots three times more than a LCA at MTOW and EW.  The LCA with so little control devices will of course be able to pitch, yaw and roll like any fighter, its Viggen`s style wing will retard vortex burst by delaying its formation and therefore flow separation. however its wings can not use flaps as freely as a fighter like the J-10 which already has canards trimming and adding extra lift when the flaps are deployed. The LCA sensitivity to supersonic center of lift shift also is greater, its wing also lacks the extra lift a canard has nevertheless the LCA is not very fast, the J-10 is faster as fast a MiG-29.  The Canard and a delta wing are draggier than a tailess wing however the J-10 also has enough thrust to overcome their unconvinience see that the J-10 is at least 3000kg heavier and has a much more powerful engine. Its true that the combined lift of a canard wing configuration is lower at cruise flight than the sum of individual lifts, however at high AoA the main wing has greater lift than it would have without it Last edited by MiG-23MLD; 5th July 2008 at 20:45.
|
|
#161
4th July 2008, 00:54
|
||||
|
||||
|
Quote:
|
|
#162
4th July 2008, 10:53
|
|||
|
|||
|
Quote:
All values behind 20 are of little practical use if at all. The top values are limited to a very small part of the flight envelope and the pilot is restricted to obey several limitations or he will depart "controlled" flight. AoA is an issue, because it is used to be a yardstick about carefree behavior, when a fighter is pushed to the limits and even behind the allowed ones like the claimed 25 AoA f.e. So it is up to the user, which limits he will enforce for operations. The MiG-29 and Su-27 are termed as carefree fighters related to that. Despite that claim, a careless pilot can force a MiG-29 into a flat-spin f.e. Looking into the instruments of a Russian Su-27. The critical AoA is 33°. The scala does end at 30°. The red-line or max allowed value is 27,5°, when the red-zone do start at 22,5°. The typical misunderstanding about flight performances are, that not all best values can be reached at the same time. Every producer is eager to publish top values reached, when the buyer has to figure out the practical benefit from that. The people here are restricted to such published values and do use that as yardsticks in general. They do not even bother to find out, how such peak values were achieved or what is the deeper sense about such claims.
|
|
#163
5th July 2008, 06:10
|
||||||
|
||||||
|
Quote:
Quote:
Elevons means the surfaces can act both as ailerons or elevators in different times. Quote:
I never seen the J-10 droop its canards like you claim. It would not have been mechanically possible. Quote:
In fact, the Soviet Union, Western Europe, and the US have all abandoned the pure delta form for one reason or another. Are you saying that the DRDO is smarter than all these countries collectively? Quote:
Quote:
__________________
pb:: Last edited by crobato; 5th July 2008 at 06:29.
|
|
#164
5th July 2008, 07:16
|
|||
|
|||
|
Quote:
As per page 7 of the technical document posted earlier, the Tejas has achieved 55 to 87 degrees AoA under scale model tests. The model was 1:15 the size of the actual and it was tested in a vertical tunnel. However, as per the same document the Tejas has been flight-tested to 20 degrees AoA, with 22 degrees never having been exceeded. Thus, it is in conformance with the global 'norm' of AoA i.e. between 20 to 25 degrees only. As per the canit.se link posted by you, the Gripen too has a preliminary alpha limit of 20 degrees (equal to Tejas' limit), exceeding which, the flight-control instantly tries to bring it down to 20 degrees or lesser (similar to how 22 degrees has been touched by Tejas). The 55 degrees limit as mentioned was the software limitation only, and it is unlikely that the airplane will actually touch that limit in tests. The article mentions that the computer will limit the alpha to angles that are sustainable keeping in view the loading, speed, altitude etc. Quote:
The Tejas also has a compound wing. However, this is often referred to as the 'crank arrow' wing in NASA research papers posted earlier, and which was the reason of "confusion" between MiG-23 MLD and me as to what actually constituted the crank on Tejas. The F-16 XL, is specifically termed as the 'crank arrow' wing. However, that is called as the compounded delta by Tejas' designers and which is explicitly referred in this research paper as the 'cranked arrow'. Hence, it may be reasonably concluded that in western academia, the compound delta is referred as the crank or 'cranked arrow'. However, in the article, "Radiance of Tejas", the Tejas' compounded wing nature is acknowledged distinctly from the crank. Hence, the crank in Tejas' context is not the compound of the wing. Now, earlier MiG-23 MLD referred to a sharp anhedral 'notch' of the wing as the crank, and which was also the definition as per another technical paper posted by me earlier. Seen from the side view, the lower-swept edge of Tejas' leading edge has a slope. Seen from the front-view, it appears as a dihedral. This may be viewed as an '"upward notch", which is likely to be the crank. Thus, the crank on the Tejas is the 'slope' or anhedral notch on the lower-swept part of the leading edge. This crank generates a low-pressure over the wing, assisting lift. It is beneficial in low altitude stability and manoueverability also. It must also be noted that such a feature is NOT found on any fighter plane developed since 1970s to date, be it Viggen, F-teens, Russian planes, or the present Eurocanards.
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A. Last edited by Abhimanyu; 5th July 2008 at 07:21.
|
|
#165
5th July 2008, 09:29
|
||||
|
||||
|
Quote:
The Rafale has its canards quit close too its wings, this has to do with the influence they have upon the wing, too far from the wing also means less benefitial effects upon the wing.  The Canards in the Lavi have also dihedral but also they are far too close to the wings in fact over them see   The Eurofighter`s are not as close to the wings as those on the Lavi, the position has to do with drag/lift ratio, the best combination is high aspect canards low aspect wings check the Eurofighter has also strakes  in the chinese J-10 also the canards are not too far from the wing, however are not so close as those in the Lavi and Rafale, the J-10 follows the lines of the interceptor while the Lavi of a fighter attack aircraft, both the Eurofighter and J-10 have the least drag canard delta wing configuration specially good for a fast aircraft  the Viggen has low aspect wings and canards, these low aspect canards and wing are best configured for high lift, while the eurofighter`s are for low drag  LINK BETWEEN THE WING AND CANARD FOR FLUTTER REDUCTION BACKGROUND In the design of a canard airplane, it is desirable for the canard to have a large aspect ratio. For aerodynamic reasons, the plane will be faster and more efficient if the aspect ratio of the canard is larger. however this configuration increases flutter see The combination of high speed and high aspect ratio increases the tendency to flutter. Flutter is fatal and cannot be tolerated. The maximum aspect ratio of the canard of a fast airplane is limited by flutter considerations, not loading considerations http://www.wipo.int/pctdb/en/wo.jsp?...3&DISPLAY=DESC see this too Canard designs suffer large penalties in drag with low aspect ratio canard surfaces The situation is less favorable for canard designs. Although small canards of high aspect ratio produce least drag, large canards of small aspect ratio achieve the highest CLmax. Moreover, the sensitivity of CLmax and drag to canard aspect ratio leads to greater compromises in each of these areas than would be required for an aft-tail design. http://aero.stanford.edu/Reports/MultOp/multop.html Last edited by MiG-23MLD; 6th July 2008 at 04:43.
|
|
#166
5th July 2008, 09:51
|
||||||
|
||||||
|
Quote:
Thus, it may show that various design houses have varying opinions based on their own test-data. It may not be said that one design is superior to the other. Quote:
Now, as mentioned earlier, the Rafale has actuator fairings visible for the outboard segment only (as shown in the schematic of top and bottom view), whereas none are visible for the inward segment. Thus, it apparently has airelons only. However, you may be right that elevons are present on some canard-delta planes as Gripen has elevons. In this labeled diagram of Gripen, labels 94 and 96 clearly mention that they are actuators for the inboard and outboard elevons respectively (i.e. for the 2 segments of one wing). Similarly, labels 67 and 68 are also outward and inward elevons for the other wing. I now agree with you that elevons on Gripen atleast can be used in conjunction with the canards for pitching moment. As discussed earlier, the Tejas can perform a simultaneous bank and pitch manouever by deflecting one elevon more than the other, albeit both upwards : the same action can be used in the Gripen. So the pitch-up as well as roll components of the elevon motion can be provided without conflict. However, whether this property of Gripen i.e. 2 moments being provided about the lift fulcrum, results in higher pitch rates than Tejas may be a matter of experimental observation only. For, as noted earlier, canards subject the wing to a 'wash', which forces an increase in the wing's AoA to achieve the same pitch effect. Canards as seen here and here are also smaller than Tejas' larger elevons, which is not subject to any 'wash'. Again, it is doubtful whether Rafale or J-10, which do not appear to have elevons are any less manoeverable than Gripen that has them. Thus, many other extraneous aerodynamic factors may be there which we may be unaware about. Or it may also be that Gripen's inboard 'elevons' may be only flaps on the trailing edge, and the outboard ones may only be airelons. Quote:
Quote:
Canard-delta designs are the particular domain of 3 particular European companies only, and so cannot be taken as an industrial benchmark. As mentioned a few times earlier, the F-teens, Flanker and MiG series do not feature canard-deltas and are not wanting of performance. In fact, I disagree that the delta has been "abandoned" by US and Russia, because the F-22 and F-35 can be reasonably termed as tailed delta planes. But there are no indications or plans of canards being added in their current or future projects. Quote:
Quote:
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A. Last edited by Abhimanyu; 5th July 2008 at 09:58.
|
|
#167
5th July 2008, 10:20
|
|||
|
|||
|
Quote:
|
|
#168
5th July 2008, 15:23
|
|||
|
|||
|
Quote:
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A.
|
|
#169
6th July 2008, 04:32
|
||||
|
||||
|
Quote:
The canard is detrimental to both lift and static longitudinal stability. The extent of canard wake roll-up is important in the interaction, and the flatter the wake the more adverse is the interaction. Downward canard deflection may lead to increases in lift of the entire configuration, and it is observed that for small vertical separations between the surfaces the forward portion of the wing is ineffective in producing lift. It is demonstrated that the canard can directly affect the pressure distribution on the wing and application of this configuration to direct lift control and control configured aircraft are noted. ( http://stinet.dtic.mil/oai/oai?verb=...fier=AD0719742 As with total drag, the aft-tail configurations retain a small advantage over canard designs. Again, the maximum attainable lift coefficient is insensitive to tail aspect ratio while canard designs' CLmax varies strongly with aspect ratio Now see why the LCA has no tail In fact, the configuration with least drag is a neutrally stable tailless design. for an small aircraft then the Tailess design offers the least drag and most range, it will be economical, the Mirage 2000 was chosen for that reason and the LCA follows the same idea  Because of the unfavorable interference of the canard on the wing, asymmetries appear in these curves. The best aft-tail designs achieve 2% to 3% lower drag than canard designs, and although in each case relatively high aspect ratio tail or canard surfaces are preferred, the drag is insensitive to the aspect ratio of aft-tail. Canard designs suffer large penalties in drag with low aspect ratio canard surfaces The canard also is the configuration with the highest drag, however since canards are usually smaller than tailplanes are still prefered by some companies than tailplanes, however the US and Russians used LERXes as canards substitutes on aft tailed designs http://aero.stanford.edu/Reports/MultOp/multop.html Last edited by MiG-23MLD; 6th July 2008 at 04:39.
|
|
#170
6th July 2008, 07:42
|
|||
|
|||
|
MiG-23 MLD, thanks for posting the above article, as it is informative.
The canard is detrimental to both lift and static longitudinal stability. .... it is observed that for small vertical separations between the surfaces the forward portion of the wing is ineffective in producing lift. From the above, I think it is referring to 'wash' over the wing, that leaves a low-pressure over the wing. So the wing gets "starved" of air to actually deflect it and create lift. Note that this happens when the canards are deflected slightly, i.e. "for small vertical separations", as described in the article. It is demonstrated that the canard can directly affect the pressure distribution on the wing and application of this configuration to direct lift control and control configured aircraft are noted. This above is the main function of the canard i.e. creating a low-pressure above the main wing to generate lift. However, the same property is detrimental to flaps and elevons of the wing which have to trim extra efforts at higher AoA to generate lift. I think this is 'upwash' (as downwash is high-pressure airflow). Canard designs suffer large penalties in drag with low aspect ratio canard surfaces. The above is the primary disadvantage of canards. The canards in J-10, Gripen, etc. are high-aspect ratio but which still provide 2-3% more drag than tailed designs, and further still than tail-less desings. The canard also is the configuration with the highest drag, however since canards are usually smaller than tailplanes are still prefered by some companies than tailplanes, however the US and Russians used LERXes as canards substitutes on aft tailed designs. To the above I may opine that like US and Russia, India also did not adopt canards for the Tejas. However, instead of LERXs, it added an andedral crank over the lower-swept portion of the wing, and which slopes upwards as it proceeds aft.
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A. Last edited by Abhimanyu; 6th July 2008 at 07:48.
|
|
#171
6th July 2008, 10:50
|
||||
|
||||
|
Quote:
for an aircraft like the LCA no canards are needed but do not misunderstand aircraft design is part science part art and designers use different compromises to achieve the performance they need read this article and you will see that canards have advantages and disadvantages http://ntrs.nasa.gov/archive/nasa/ca...1996071178.pdf
|
|
#172
7th July 2008, 16:21
|
||||
|
||||
|
Quote:
see The straight leading edge was swept at 54 degrees, with maneuver flaps on the ourboard sections. The tips were cropped and fitted with missile rails to carry the Rafael Python 3 air-to-air missile. Two piece flaperons occupied most of the trailing edge, which was blended into the fuselage with long fillets. The wing area was 38.50 square meters, 38 per cent greater than the wing area of the F-16, giving an almost exactly proportionally lower wing loading, while the aspect ratio at 2.10, was barely two-thirds that of the F-16. Pitch control was provided by single piece, all-moving canard surfaces, located slightly astern of and below the pilot where they would cause minimal obstruction in vision. this is the aspect ratio and why the Lavi has so close its canards to its wings, for visibility and AoA handling see other factors Predictably, relaxed static stability and quadruplex fly-by-wire (FBW), with no mechanical backup was used, linked to nine different control surfaces to give a true control configured vehicle (CCV). In comparison with the F-16, the Lavi is very unstable, with an instability of 10 to 12 per cent. The surfaces were programmed to give minimum drag in all flight regimes, while providing optimum handling and agility. canards are draggier but by using relaxed stability and positioning the center of lift farther ahead from the Center of gravity than the F-16`s the Lavi fixed the draggier configuration. The powerplant intake was a plain chin type scoop, similar to that of the F-16, which was known to be satisfactory at high alpha and sideslip angles. The landing gear was lightweight, the nose wheel was located aft of the intake and retracting rearwards, and the main gear was fuselage mounted, giving a rather narrow track. The sharply swept vertical tail, effective at high alpha due to interaction with the vortices shed by the canards, was mounted on a spine on top of the rear fuselage Since canards also create flutter upon the vertical tail then the Lavi`s vertical tail has a very swept vertical tail. http://www.jewishvirtuallibrary.org/...ture/lavi.html The J-10 in that sense follows more the Eurofighter`s canard wing design The aspect ratio of course was one of the main advantages applied to the LAvi from the LERXed F-16s Performances at Supersonic Speeds Wing sweep and aspect ratio at supersonic speeds have a rather precise correlation, showing the stability limits of the wing. In this correlation the aspect-ratio decreases as the sweep increases. For sweeps of 40 to 60 degrees the aspect-ratios range is 2 to 4, although this limit can be occasionally exceeded by accurate design of the tails and other control surfaces. Since high sweep is required to fly with agility at supersonic speeds, the aspect-ratio is set as a consequence. The Table below shows a summary of fighter aircraft wing aspect-ratio and maximum speeds Table 1: Aspect-Ratios of Fighter Wings Aircraft AR M US F-15 (McDonnell-Douglas) 3.0 2.5 US F-18 (McDonnel-Douglas) 3.5 1.8 Dassault Mirage 2000 2.0 2.2 Dassault Rafale MO2 2.6 2.0 Sukhoi Su-27 3.5 2.3 Mapo Mig-29 3.4 2.3 http://aerodyn.org/Wings/larw.html Last edited by MiG-23MLD; 7th July 2008 at 16:41.
|
|
#173
8th July 2008, 05:55
|
||||||||
|
||||||||
|
Quote:
Quote:
Quote:
Aileron = two surfaces that move opposite of each other. Elevator = two surfaces that move in the same direction at each other. An elevon part times as an aileron and as an elevator. But unlike canard-deltas and tailed planes, an elevon cannot function in one moment of a time, as both aileron and elevator, because aileron and elevator is functionally an "or" proposition. Quote:
If you ever registered in the CDF, you can see this picture at the end of this thread http://www.china-defense.com/forum/i...pic=23&st=1975 at the far left corner of the picture you can see a J-10 on take off, and even with the blur, the canards are point up and not drooped, and the trailing wing surfaces are acting as elevators in the take off position. Quote:
Quote:
Quote:
Quote:
And even if they are turned to pitch, canards generate lift even for the drag they produce. Control surfaces on the trailing edge of the wings however, have to push the aircraft down on its tail to move the nose up, and hence they create negative lift while exerting drag at the same time.
__________________
pb:: Last edited by crobato; 8th July 2008 at 06:10.
|
|
#174
8th July 2008, 14:48
|
||||
|
||||
|
Quote:
The LCA is a very economical design, being tailess, it generates the least drag, flutter and weight, this configuration is good if you want small and ligt aircraft with high speed and long range, the F-16XL was for that reason considered as a fighter bomber competing with the F-15E The combination of high speed and high aspect ratio increases the tendency to flutter. Flutter is fatal and cannot be tolerated. The maximum aspect ratio of the canard of a fast airplane is limited by flutter considerations, not loading considerations http://www.wipo.int/pctdb/en/wo.jsp?...3&DISPLAY=DESC Other fighters have other design parameters, the J-10 for example followed a delta wing with low aspect ratio and high aspect ratio canards to generate the least drag and the highest speed, however the design generates flutter and inertia coupling is common in aircraft with long fuselages and short spans (low aspect ratio) wings, so dihedral in the canards allowed the least flutter, avoided vortex impinging on the leading edges and allowed better roll stability. however canard`s sizes are also limited by the flutter they generate but since they are ahead of the Center of gravity well a small size is affordable . Aircraft with short span and a long fuselage are capable of high roll rates but also prone to inertia coupling like the F-5 All airplanes turn by tilting the lift vector (banking), then increasing the lift to cause a change in the direction of flight. Highly maneuverable fighter airplanes must have an ability to generate a small turn radius, but must also have an ability to quickly change the direction of the turn. This means that the pilot must be able to change bank angle (roll) very quickly to re-orient the lift to the direction of the desired turn. Fighter aircraft with high roll rate capability often experience another coupling phenomenon known as "inertial coupling". Inertial coupling may occur if there is a large difference between the roll moment of inertia and the yaw or pitch moments of inertia for the airplane. This is often the case for fighters which have short stubby wings (low roll inertia) and long fuselages with heavy engines, electronics, fuel, etc. (high pitch and yaw inertia). When such an airplane is exposed to high roll rates along the fuselage axis, the high mass concentration along the fuselage may cause it to behave like a "dumbbell". The centrifugal force due to the roll will cause the nose and tail to try to swing out perpendicular to the rotation axis http://www.dfrc.nasa.gov/Education/O...t/nasroll.html Flutter, drag and relatively low sustained turn rates are the drawbacks of delta canard designs. The results are aircraft with good agility and high speed such as the J-10. Tailplanes need relatively low deflections since they also are under the downwash of the wing and this generates a down force, tailpanes also are pitch and roll devices, so canards are not better in that sense the only real advantage a canard has is at high AoA allowing the wing to have extra low presure and attaching the flow to the wing effectively reducing the AoA. The advantage of the tailplane is in flutter and drag and with LERXes well more or less get the best of the canard, nevertheless the LERXs also generates flutter and the F-18 suffered vortices flutter Flutter Excitation One of the most dangerous events that can occur in flight is a phenomena called "flutter". Flutter is an aerodynamically induced vibration of a wing, tail, or control surface that can result in total structural failure in a matter of seconds. The prediction of flutter is not a precise science and requires flight verification that flutter will not occur within the normal flight envelope. http://www.dfrc.nasa.gov/Education/O...t/nasflut.html See the J-10 has short wings and a relatively long fuselage  Last edited by MiG-23MLD; 8th July 2008 at 17:21.
|
|
#175
11th July 2008, 07:40
|
||||||
|
||||||
|
Quote:
I stand corrected that the US and Russia have indeed experimented at least on the canard-delta designs. I was aware of X-31, however while typing the post it escaped my recall. Quote:
Besides, it may also be noted as per the research paper posted by MiG-23 MLD (and various others available) that the experimental delta F-16 XL was concluded to be superior to the F-15 that was in service; however, the "momentum" with the F-15 was begun and so commitment towards it was not changed. Quote:
A delta plane can thus perform ALL the manouevers performable by a conventional tailed plane, as well as canard-delta plane. Quote:
Actually presently canards in all planes are hinged (unlike Viggen's canards, which were fixed and that had "elevon" like structures at aft). As I am unable to view the photo from CDF, you may please post it on this thread. Quote:
However, during flight, they are not seen trimming as much as shown in the photos because small trims suffice to achieve the manouevers. In contrast, smaller control surfaces have to trim more to achieve the same effect if they are the primary pitch authority; if assisted by elevons even if 'washed', the trim may not be as much. To illustrate the importance of sheer size as a counter example, one may 'imagine' had the elevons on Tejas been 50% of their area (same as a canard's size on the J-10). By this basic flight manouevers may have been impossible. Quote:
I think the debate may not be continued further, as it is increasingly descriptive and speculative now. In my view, the J-10 and Tejas are likely to have equal agility.
__________________
Tejas Mk.2 for MRCA. .. .. .. .. Reject PAK-FA for M.C.A.
|
|
#176
11th July 2008, 20:57
|
||||
|
||||
|
Quote:
The debate is not highly speculative simply you do not want to see realities, all the fourth generation fighters built after 1980 have tails or canards either in Europe, Russia or the US 1970 F-14 has tail 1971 F-15 has tail, Kfir has canards 1974 F-16 has tail 1977 MiG-29 and Su-27 have tails 1978 F-18 has tail 1978 Mirage 2000 has strakes (strake a mini canard in fact), tailess tough; Mirage 4000 has canards 1982 F-16XL tailess 1984 X-29 has canards 1986 Rafale has foreplanes, EAP has canards 1988 Gripen has foreplanes, Su-35 has canards and tailplanes 1990 YF-22 has tail;YF-23 tailess (winner YF-22), X-31 has canards 1994 Eurofighter has foreplanes 1997 J-10 has foreplanes; S-37 Berkut has canards and taiplanes (Su-47), F-22 has tail 2000 MiG1.44 has canards. 2001 LCA tailess Each aircraft has compromises The F-16 for example is better than the Mirage 2000 at low speeds and altitudes but at some speeds and altitude the Mirage 2000 is better than the F-16, same is even with the MiG-23 at some very high speeds and altitudes its wings allowed it to have a slight advantage over the F-16 It is not different case with the J-10 and LCA, it is almost a fact the J-10 is better at low speeds and altitudes due to its canards but there must be some speeds and altitudes were the LCA might have an advantage, however the J-10 very likely has the best ITR and corner velocity. The J-10 also must be a good roller, a good aircraft in terms of instataneous turn rate (ITR) but due to its delta wing not a good aircraft sustaining a turn. If you fly against a J-10 in a MiG-29 it will be difficult to keep the chase since the J-10 is a good roller will change direction very quickly and initiate a turn at a very fast angular velocity but it won`t keep that angular velocity long in that is better very likely the MiG-29, once in the turn the MiG-29 will probably surpass the J-10 If you see tails and canards are more used and the reason is flaps are used more freely with either one of them, tailess designs have too much compromises using the flaps Last edited by MiG-23MLD; 12th July 2008 at 01:57.
|
|
#177
11th July 2008, 22:53
|
|||
|
|||
|
Can we please give this canard vs non-canard thing a rest?
None of us have the data needed to make even reasoned speculations on this topic: just because designs W, X and Y use canards doesn't mean that it is suitable for design Z. We have no idea about LCA's inertial tensor, wing performance (pitching moments, vortex formation), effects of elevon sizing, wetted area/parasitic drag, etc. Presumably, the people who designed the LCA had access to this data. We know that they evaluated canards and rejected the idea. So, the debate comes down to: a) the designers are incapable idiots, because all 4'th gen fighters after 1980 must have tails or canards, and performance will suck otherwise. (Gee --- maybe we should get them a subscription to AFM so they can keep up with the times.) b) we take the designers on their word that they performed the trade studies and concluded that the canards weren't necessary for meeting the aircraft's requirements
|
|
#178
12th July 2008, 01:50
|
||||
|
||||
|
Quote:
All your argument is a total desire to remain ignorant, the vast majority of statements here are based upon studies by NASA and if you go a read the whole thread, you will see that all the studies by NASA posted here point out the advantages of Tailplanes and Canards versus tailess in most areas except drag. Of course you will say but we do not have this and that information, that is just a way to deny a reality, to claim the secret data makes the LCA better than the Eurofighter or Rafale, that is just plain trash. The LCA was designed with a set of specifications and compromises, this means the following by choosing the tailess configuration, the LCA gained in some areas but gave up other advantages, this trade off has been balanced by its weapons system and avionics. Of course your secret data for you makes the LCA the super agile fighter, its Viggen style delta wing makes it good at everything for you, but saddly man it is not true, the LCA lost some advantages that canards give but in other ways it gained, the reason you make a tailess aircraft is simple. The Mirage 2000 like the LCA have lower thrust to weight ratios than the F-16 or MiG-29, however they have lower drag than the tailed or canard designs and that is the reason why they are still competitive, however. in the case of India some design limits made them choose the tailess configuration however those who dream their national fighter has not trade off imagine the LCA as the super secret aircraft, with secret data that makes it better than the Eurofighter and of course just not to stay behind the J-10. Realities are realities and the LCA is a good aircraft but it has limits and those who prefer being ignorant just to keep their national pride have chosen that by their own will, in my case i can tell you i prefer to believe NASA why do you think the Mirage 2000 has no canards but strakes? see that strakes more or less are mini canards, answer because the strake generates also a vortex but generates less drag, the low thrust to weight ratio of the Mirage 2000 made canards excesively draggy and strakes were choesen instead claim: 1. An apparatus attached to an aircraft that has a fuselage, a pair or wings extending from the fuselage and a pair of nacelles interposed between the fuselage and the wings, comprising: a pair of strakes each rigidly attached to an engine nacelle forward and above the wing, said strakes having an area aspect ratio such that vortices are created along the wing roots on the aircraft to increase the lift of the wings when the aircraft is flying at an angle of attack. 4. An apparatus attached to a T-38 aircraft that has a fuselage, a pair of wings extending from the fuselage and a pair of engine nacelles interposed between the fuselage and the wings, comprising: a pair of strakes each rigidly attached to an engine nacelle forward and above the wing, said strakes having an area aspect ratio such that vortices are created along the wing roots of the aircraft to increase the lift of the wings when the aircraft is flying at an angle of attack. Prior Art A modern high performance jet aircraft of simple configuration typically is comprised of a fuselage, swept back wings of a delta or trapezoidal configuration, and horizontal and vertical tail surfaces. Typically such basic configurations perform relatively well, though frequently it is desired to improve certain aspects of operation or performance thereof. Two aspects frequently sought to be improved are operation at lower speeds and higher angles of attack, and the enhancement of the stability and control of the aircraft. Wing lift has also been increased in the past by adding a leading edge extension to the wings in the root area. While this somewhat increases the wing area, it also allows operation of the aircraft at higher angles of attack, thereby primarily increasing the coefficient of lift for the wing through an increase in the angle of attack. Such leading edge extensions typically are in the plane of the wing, and simply extend the wing forward in the root area thereof. In still other situations, strakes have been used for various purposes, sometimes only fully appreciated by the designers that added the same to the basic aircraft configuration, the strakes correcting some undesired local flow or somehow controlling the flow to obtain some desired effect not otherwise inherent in the basic aircraft configuration. By way of specific example, the Mirage 2000, a French delta wing aircraft, has a small strake above and just forward of the wing root, the purpose of which is not apparent as the same is too small for any meaningful lift enhancement. A similar small strake appears on an Israeli modification of the Mirage, a delta wing aircraft as well. Similar strakes have heretofore not been used on trapezoidal wing aircraft. On the other hand, on the McDonnell Douglas MD-80 commercial airliner, small wing-like strakes are positioned well forward on the fuselage, much like a Canard configuration. On the DC-10, strakes are used on the engine housings under the wings thereof. http://www.freepatentsonline.com/5249762.html  Overall Configuration The Mirage 2000 first flew on 10. March,1978. It was designed to fulfill a requirement for a high flying interceptor. The Mirage 2000 strongly resembles the Mirage 3 in most respects. One visible addition to the airframe are the small strakes attached to the air-intakes. They create vortices that energise the airflow over the wing http://www.mirage-jet.com/AIRFRAME/airframe.htm As part of a combined experimental and analytical study of vortex shedding at sharp edges characteristic of strakes on fighter aircraft, numerical simulations were made of a two-dimensional and a three-dimensional case. The former is a sharp-edge flat plate normal to the flow, for which some experimental data were taken earlier in this program. http://stinet.dtic.mil/oai/oai?verb=...fier=ADA125882 Vertical nose strake for aircraft stability and control Document Type and Number:United States Patent 5449131 Abstract:A pivotal strake located at the nose section of an aircraft forebody. The strake pivots about an axis that is essentially perpendicular to the surface of the nose section http://www.freepatentsonline.com/5449131.html this is for an aircraft like the X-29 http://www.nasa.gov/centers/dryden/i...n_X-29_330.jpg  Last edited by MiG-23MLD; 12th July 2008 at 03:02.
|
|
#179
12th July 2008, 07:22
|
|||
|
|||
|
MLD,
Thanks for your fantastic rant (suitably illustrated, as always) --- please also accept my congratulations for your keen ability to point out my inherent propensity for self-delusion and ignorance. Now go back and read my post and point out exactly where I made any claims about the relative performances of LCA, Rafale, etc. Let me repeat my claims: a) The LCA designers fixed the current configuration by performing trade studies that established that it is better than a canard configuration at that design point. b) The relative performance of any two aircraft (be they LCA/EF/Rafale/J10/F22 whatever) cannot be judged by just looking at configurations. You need a lot more data than that --- data that we don't have access to.
|
|
#180
12th July 2008, 19:47
|
||||
|
||||
|
Quote:
All this speech i know it, first you have to tell why an aircraft has some advantages having canards or tailplanes or simply being tailess. If you read the thread you will find some articles taken from NASA which explain what each configuration offers and what are the trade offs. Now you can guess more or less just by seeing the configuration and knowing the thrust to weight ratio that the LCA is not very different from the Mirage 2000. yes it has differences but its basicly the same concept, the J-10 is more in line with the F-16. Let us start with its basic design, the inlets seem very similar to those fitted to the F-18, also the wing works and interacts with the inlet similarly to what the F-18`s LERXes do at AoA. Since both aircraft have the same engine we have to guess the inlets have similar performance in the F-18 and LCA, with its simple fixed vertical ramp however they are smaller since it uses only one engine instead of two   If the LCA does not use canards it does not mean canards are not good or it has not trade offs by being a tailess design, for its specifications being a tailess aircraft makes it more practical than using canards however the trade offs of being a tailess design are in stability. specially longitudinal stability Last edited by MiG-23MLD; 12th July 2008 at 19:55.
|
 |
| Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
| Thread Tools | |
| Display Modes | |
|
|
Linear Mode
